Version 23.1 of the ETC was delivered in advance of the Cycle 23 call for proposals, and contains several updates to both the COS and STIS ETC pages. More details can be obtained through the release ETC notes, known issues, and user guide.

Of particular note for the spectroscopic STIS page is the inclusion of three newly supported slits primarily for the NUV- and FUV-MAMA echelle gratings: 31X0.05NDA, 31X0.05NDB, and 31x0.05NDC. In order to support calculations of ACQ/PEAK exposures, these slits are also available for the target acquisition STIS ETC. For all STIS ETC pages the dark rates for the FUV- and NUV-MAMAs, and the dark rate and read-out noise for the CCD have been updated to reflect the latest performance of the instrument. Throughputs for all STIS modes have also been updated to reflect the expected throughput at mid-cycle 23, or March 15, 2016.

For COS, stripe specific signal-to-noise ratios are now reported for the COS Spectroscopic Acquisition ETC for the NUV PeakXD mode. This will enable users to more accurately choose which stripe they want to use for a given NUV PeakXD exposure. For all COS ETC pages detector and segment-specific dark rates have been updated, using values that encompass 95% of observed dark rates. Throughputs for all COS modes have also been updated to reflect the expected throughput at mid-cycle 23, or March 15, 2016.